This invention relates generally to the electrical lead connection between the spark plugs and the magneto of an internal combustion engine, and in particular to said lead connection for use in the aviation industry. It is well known in the aircraft engine art that a tendency exists for moisture and dirt to interfere with the connection between the spark plug and harness lead or between the harness lead and magneto, thereby resulting in misfiring of the plug and corollary poor engine performance.
Moisture proofing of the terminal connections is hampered somewhat by the physical construction of the lead wires or cables. Said cables are normally made with a center conducting core such as copper, insulated, shielded, with a woven metal braid, and again covered with insulation. The shielding braid is necessary to prevent radio interference from the ignition system, and even minor twisting of the braid during installation permits spurious electromagnetic radiation to escape.
There have been numerous efforts by inventors in the field to provide moisture-proof terminal connections for the leads. Of note are the terminal means disclosed in U.S. Pat. No. 3,262,085, issued July 19, 1966 to F. S. Slick and in the U.S. Pat. No. 3,334,326, issued Aug. 1, 1967 to C. D. Besore, et al.
The Slick patent discloses the use of a resilient helical compression spring connected to the cable core as an improved contact terminal for connection to a magneto.
The Besore invention discloses a moisture-proof connector for aircraft spark plugs which have an externally threaded cylindrical barrel encasing the plug insulator and contact. The connector basically comprises an electrical cable covered with insulation and having contact means at one end thereof for engagement with the plug contact terminal. A tubular grommet of resilient material adapted to fit within the plug barrel is positioned on the cable end adjacent the contact means for providing a moisture-proof barrier when inserted in the cylindrical band. A rigid ferrule and nut are placed on the cable above the grommet for securing the cable to the barrel.
Present aircraft harness leads on the market are inserted through the magneto distributor housing, the shielding flared, and held in place with a ferrule inside the housing. This particular arrangement understandably creates considerable difficulties should replacement of the lead be required.
It is therefore an object of this invention to provide a new improved harness assembly and magneto block which are moisture-proof, facilitate the quick replacement of the harness lead, if necessary, and provide improved electrical connection without distortion of the shield wire.